Olfactory sensory neurons (OSNs) have been studied due to their relationship to disease processes, for example, Alzheimer's disease and other neurodegenerative diseases. Initial symptoms may include a decreased sense of smell due to OSN loss and/or processing impairments of sensory circuits. Studies have shown a decrease in OSN neural density in the olfactory epithelium of Alzheimer's patients, while others have attributed neuron loss in other regions of the sensory circuit as a source of olfaction deficits. Although biopsies of the olfactory epithelium offer potential for OSN analysis in living humans, these biopsies do not offer a global picture of the OSN neural density status in a patient, and they have a large sample bias that can make it difficult to interpret the results.